Preparation of polyurethane foam from 1-{2[bis(2-hydroxypropyl)amino]ethyl}-4-(2-hydroxypropyl) piperazine



United States Patent PREPARATION OF POLYURETHANE FOAM FROM1-{2[BIS(2-HYDROXYPROPYL)AMINO]ETHYL}-4- '(2-HYDROXYPROPYL)PIPERAZINEVernon A. Currier and Michael Cuscurida, Austin, Tex.,

assignors to Jefferson Chemical Company, Inc., Houston, Tex., acorporation of Delaware No Drawing. Original application July 16, 1962,Ser.

No. 210,222. Divided and this application Feb. 26,

1965, Ser. No. 435,704

4 Claims. (Cl. 260-25) This application is a division of copendingCurrier et al.

application Serial No. 210,222, filed July 16, 1962, and

entitled, New Compound and Method for Preparing Polyurethane Therefrom.

This invention relates to a new polyfunctional compound, a method forpreparing the compound, a foamed polyurethane made therefrom and amethod for preparing the polyurethane therefrom.

It is known to prepare rigid polyurethane foams by reacting apolyfunctional polyol with an organic polyisocyanate in the presence ofa blowing agent and a catalytically effective amount of a low molecularweight acyclic or heterocyclic aliphatic tertiary amine. However, theuse of amine catalysts of this nature has not been entirely satisfactorybecause of the objectionable odor that is frequently imparted andbecause of their cost.

It has now been discovered that the foregoing and related problems canbe significantly overcome through the provision of a new asymmetricalpolyfunctional compound containing not only secondary hydroxyl groupsbut also tertiary nitrogen groups; such compound having good reactivitywith rigid polyurethane feed materials to thereby provide rigidpolyurethane foams.

The new compound is 1-{2[bis(2-hydroxypropyl)-amino]ethyl}-4-(Z-hydroxypropyl)piperazine. The compound is easilyprepared by bringing propylene oxide into contact withN-aminoethylpiperazine at a temperature in excess of about 50 C. Thereaction proceeds non-catalytically and terminates after the reaction ofthree mols of propylene oxide with each mol of N-aminoethylpiperazine toquantitatively provide the new compound of the present invention(hereinafter referred to as pr-opoxylated N- aminoethylpiperazine) s.

It has also been discovered that rigid polyurethane foams can beprepared by reacting an organic polyisocyanate in the presence of ablowing agent and a foam stabilizer with an equivalent amount of ahydroxyl component consisting essentially of from about 30 to 90 wt.percent of the propoxylated N-aminoethylpiperazine of the presentinvention and, correspondingly, from about 70 to about wt. percent of apolyol having an average of at least three terminal hydroxy groups andhaving a hydroxyl number within the range of about 250 to about 750,said polyol being selected from the group consisting of polyhydricalcohols and linear polyesters having terminal hydroxy groups, whichpolyesters are obtained from reaction of a polycarboxylic acid with apolyhydric alcohol. The polyhydric alcohol may be a polyether obtained,for example, by the ethoxylation or propoxylation of a trihydric,tetrahydric, etc., aliphatic alcohol;

The results obtained in the preparation of rigid polyurethane foams inaccordance with the method of the present invention are trulysurprising. Thus, for example, unsatisfactory results are obtained withclosely related compounds. For example, the compoundtrimethylaminoethylpiperazine is not a highly effective urethanecatalyst. Propylene oxide condensates of aliphatic amines such as thetetrapropylene oxide condensate of ethylenediamine have insuflicientactivity on a weight basis to give equivalent results with equivalentformulations. This is like- 3,251,788 Patented May 17, 1966 ice wisetrue if the propoxylated N-aminoethylpiperazine is compared with thefour mol propylene oxide condensate of ethylenediamine on a mol basis.

As has been indicated, the novel compound of the present invention is athree mol propylene oxide adduct of aminoethylpiperazine having thesystematic name 1-{2- [bis (2 hydroxyp-ropyl)aminojethyl} 4 (2hydroxypropyDpiperazine and having the formula:

As will be observed from the above formula, the new compound of thepresent invention is asymmetrical and contains a heterocyclic ringstructure. It is also to be observed that the compound contains threetertiary nitrogen atoms; that one of the nitrogen atoms is substitutedwith two beta-hydroxypropyl groups; that another nitrogen atom issubstituted with a single beta-hydroxypropyl group and that the thirdnitrogen atom is free from substituent beta-hydroxypropyl groups.

The new compound with the present invention is easily prepared by thenon-catalytic reaction of three mols of propylene oxide with one mol ofN-aminoethylpiperazine. The reaction is preferably conducted at atemperature above 50 C. Although stoichiometric amounts of proplyeneoxide and N-ami'noethylpiperazine may be used, it is normally preferableto utilize an excess of propylene oxide since the non-catalytic reactionis self terminating after the reaction of three mols of propylene oxidewith each mol of N-aminoethylpiperazine. That is, after the amine activehydrogen atoms have reacted with propylene oxide, no additionalpropoxylation occurs at the hydroxyl groups.

When the compound of the present invention is to be utilized in thepreparation of rigid polyurethane foams, the other ingredients for thefoam formation steps include a polyisocyanate, a polyol, a blowing agentand a foam stabilizer.

The preferred class of polyisocyanates to be utilized are the organicpolyisocyanates, such as toluene diisocyanate, 2,4-diisocyanate,cyclohexylene diisocyanate, phenylene diisocyanate, diphenylmethanediisocyanate, 3,3- dimethyl-4,4'-biphenylene diisocyanate,tetramethylene diisocyanate, hexam ethylene diisocyanate,m-xylylene-l,3- diisocyanate, 2,6-diethylbenzene-1,4-diisocyanate,3,3-dimethoxydiphenyl-methane-4,4' diisocyanate, etc., and mixturesthereof.

The polyolto be utilized should preferably be a polyol 7 containing atleast three terminal hydroxy groups. Moreover, the polyol shouldsuitably have a hydroxyl number within the range of about 250 to about750.

One class of polyols that may be utilized are polyethers prepared by thepropoxylation of a triol, such as glycerine, hexanetriol, etc.; atetrol, such as pentaerythritol, alpha-methyl-D-glucoside; a pentol,such as arabitol, xylitol, adonitol and anhydroenneaheptitol; or ahexol, such as sorbitol and mannitol.

Another class of polyols that may be utilized successfully are thehydroxy terminated polyesters prepared by reacting a polyhydric alcoholwith a polycarboxylic acid and having a molecular weight within therange of about 400 to about 4000. Typical polyesters of this natureinclude polyethylene adipate, polypropylene succinate,poly-1,2-propylene adipate, polyethylene succinate,-polyethylenesebacate, polyethylene azelate, diethylene glycoldimerized linoleicacid, polypropylene glycol-dimerized linoleic acid, and mixturesthereof. Also included would be polyfunctional glycerine ortrimethylolpropane-diethylene glycol or propylene glycol condensationproducts. These esters are conveniently prepared by reacting the glycoland acid components at a temperature within the range of about 120 toabout- 210 C. to remove water partially and to provide a polyesterhaving active hydroxyl hydrogens at the end of the polyester chain.

As has been indicated, the propoxylated N-aminoethyl piperazine of thepresent invention should comprise from about 30 to about 90 wt. percentof the hydroxyl components of the polyurethane manufacture, and thepolyol should constitute the remaining 70 to wt. percent.

ing agent of the type known to those skilled in the art. Thus, normallyliquid halogenated aliphatic hydrocarbons, monochlorotrifluoromethane,dichlorodifluoromethane, etc., may be utilized as desired.

Similarly, the foam stabilizer may be any of the foam stabilizers knownto those skilled in the art, including silicone glycol copolymers,dimethyl polysiloxane, polyethoxylated vegetable oils, polyethoxylatedfatty acids, polyethoxylated phenols, polyethoxylated sorbitanmonoesters and sorbitan monoesters.

The polyisocyanate and polyols should be proportioned so as to providefor substantially equivalent amounts of the two ingredients. Preferably,however, a slight excess of polyisocyanate is employed. The blowingagent should be used in amounts sufficient to provide for a foam of adesired density. For example, with respect to halogenated aliphatichydrocarbons such as chlorofluoromethanes, the blowing agent maycomprisefrom about 5 to about wt. percent of the combined Weight of polyol andpolyisocyanate.

The foam stabilizer, which is preferably but not necessarily employed,should be used in a stabilizing amount (e.g., from about 0.01 to about 5wt. percent, based on the total weight of charged materials).

The reaction between the isocyanate groups and hydroxyl groups is highlyexothermic. Therefore, in accordance with established practice it isgenerally preferable to prepare a mixture of the propoxylated N-aminO-ethylpiperazine of the present invention with the polyol, blowing agentand foam stabilizer and then to add rapidly the polyisocyanate to themixture with good agitation.

Because of an exothermic nature of the reaction, the heat that isliberated will cause a blowing of the foam. Suitably, the reaction ratesshould be of a nature such that the foam rises to a stable height withinabout 5 to about .150 seconds after mixing of the organic polyisocyanatewith the other ingredients for the foam preparation.

characteristics whereby post curing can be minimized. The invention willbe further illustrated by the following specific examples which aregiven by way of illustration and not as limitationson the scope of thisinvention.

EXAMPLE I Preparation of propoxylated N-aminoethylpiperazineAminoethylpiperazine (14.5 pounds, 0.112 pound mol) was charged to afive-gallon stirred autoclave. Air was removed by flushing the kettlewith nitrogen or natural gas. The amine was heated to 110 C. andpropylene oxide added with stirring. During the addition of propyleneoxide the temperature was maintained at 110 C., and the pressure Was notallowed to exceed 60 p.s.i.g. Approximately 2 /2 hours were required forthe addition of 19.7 pounds (0.339 pound mol) of propylene oxide. Theproduct was stirred and heated at 110 C. for an additional hour afterallof the propylene oxide The blowing agent to be used may be anysuitable blow- Surprisingly, polyurethane foams of a rigid natureprepared by the present invention have good stability had been added.The propoxylated amine was a light colored viscous liquid having thefollowing properties:

Primary amine meq./g 0.1 Secondary amine meq./ 0.0 Tertiary amine meq./g6.50 Hydroxyl number 551 Color (APHA) pH (1 wt. percent aqueous) 10.8

EXAMPLE 11 Preparation of rigid foams based upon propoxylatedN-aminoethylpiperazine As an indication of the excellent catalyticactivity of the compound of the present invention, an attempt to preparea polyurethane foam by reactive compound of the present invention withan equivalent amount of toluene diisocyanates in accordance with theso-called oneshot method resulted in an unstable foam, since the.

foams formed by the reaction had an excessively, rapid rise time ofabout four seconds as compared with the chain extension reaction timewhich was considerably slower.

EXAMPLEIII As another example of the excellent catalytic activity of thecompound of the present invention, an attempt to prepare a rigid foam bythe so-called quasi prepolymer method was unsuccessful. Thus, mixing ofthe propoxylated N-aminoethylpiperazine with toluene diisocyanate'caused the formation of a gel.

EXAMPLE IV A good polyurethane rigid foam was prepared by the followingprocedure:

Components in parts by weight used to prepare the rigid urethane foamwere as follows:

All of the components except the toluene diisocyanate were stirred at900 rpm. for one minute. Toluene diisocyanate was added and the mixturewas stirred for an additional ten seconds and the product poured into amold. The rise time was 35 seconds, and the maximum internal temperatureof the foam was 183 C. v The product, after curing at room temperature,was a nontacky rigid foam.

EXAMPLE V Components in parts by weight used to prepare the rigid foamwere as follows:

Propoxylated N-aminoethylpiperazine 30 Oxypropylated glycerine of 400M.W .70 TDI 65 Halogenated methane .25 Silicone 1.5

formulation containing the smallest amount ofpropoxylatedN-aminoethylpiperazine had the longest 'use time. This is due to thesmaller amount of catalyst in the form of the tertiary amine groups inthe propoxylated N-aminoethylpiperazine.

EXAMPLE VI The preceding example was repeated except that an equalweight of the tetrapropoxyderivative of ethylenediamine was substitutedfor propoxylated N-aminoethylpiperazine, and except that 77.8 parts ofthe toluene diisocyanates were employed.

In this situation, the product had a rise time of about 90 seconds and amaximum internal temperature of the foam of about 154 C. Moreover, thefoam suifered a partial collapse.

From this it is seen that the propylene oxide condensate ofethylenediamine was not as eflective as the compound of the presentinvention for the preparation of polyurethane foams.

What is claimed is:

1. A method for preparing a rigid polyurethane foam which comprisesreacting a hydroxy component with an excess of an organic polyisocyanatein the presence of 5 to 15 wt. percent of a blowing agent and 0.01 to 5wt. percent of a foam stabilizer based on the combined weight of thehydroxy component and the polyisocyanate, said hydroxy componentcomprising 10 to wt. percent of a polyol having a hydroXyl number in therange from about 250 to 750 and from about to 30 wt. percent of1-{2[bis(2-hydroxypropyl) amino]ethyl}-4- (Z-hydroxyprbpyDpiperazine.

2. A method as in claim 1 wherein the polyol is a polyether polyol.

3. A method as in claim 1 wherein the polyol is a linear polyesterhaving terminal hydroxy groups.

4. A method as in claim 1 wherein the blowing agent is a normally liquidhalogenated aliphatic hydrocarbon.

References Cited by the Examiner UNITED STATES PATENTS 2,995,530 8/1961Frisch 2602.5 3,075,927 1/ 1963 Lanham 2602.5 3, 1 12,28 1 11/ 1963Gromacki 260-2.5

LEON J. BERCOVITZ, Primary Examiner.

DONALD E. CZAJA, Examiner.

1. A METHOD FOR PREPARING A RIGID POLYURETHANE FOAM WHICH COMPRISESREACTING A HYDROXY COMPONENT WITH AN EXCESS OF AN ORGANIC POLYISOCYANATEIN THE IN THE PRESENCE OF 5 TO 15 WT. PERCENT OF A BLOWING AGENT AND0.01 TO 5 WT. PERCENT OF A FOAM STABILIZER BASED ON THE COMBINED WEIGHTOF THE HYDROXY COMPONENT AND THE POLYISOCYANATE, SAID HYDROXY COMPONENTCOMPRISING 10 TO 70 WT. PERCENT OF A POLYOL HAVING A HYDROXYL NUMBER INTHE RANGE FROM ABOUT 250 TO 750 AND FROM ABOUT 90 TO 30 WT. PERCENT OF1-(2(BIS(2-HYDROXYPROPYL)AMINO)ETHYL)-4(2-HYDROXYPROPYL)PIPERAZINE.